Article Figures & Data
Figures
- Figure 1.
Experimental setup, field recordings, and intracellular recordings. A, Illustration of the experimental setup including relevant afferent and efferent cerebellar pathways. As the CS, we stimulated the forelimb, mossy fiber (MF), or superior colliculus (SC). As the US, we stimulated CFs. DN, Deep nuclei; GC, granule cell; NO, nucleo-olivary; PC, Purkinje cell. B, Typical examples of field potentials elicited on the cerebellar cortex following stimulation of cerebellar afferents. C, Representative sweeps from intracellular recordings showing that the number of elicited EPSPs in Purkinje cell dendrites corresponds to the number of stimulus pulses applied to the climbing fibers, and that peripheral, periorbital stimulation elicits multiple EPSPs.
- Figure 2.
A single-pulse CF stimulus results in extinction of the Purkinje cell CR. A, Extracellular Purkinje cell recording from a single cell showing responses to the conditional stimulus before and after training with a single stimulus pulse. B, Raster plot showing the gradual extinction of a Purkinje cell CR during training with a single stimulus pulse. The acquired pause response initially appears to last beyond the US, and as the pause response is extinguished it is replaced by a US-induced excitation. Each dot represents one simple spike in the extracellular record, and each line represents one trial. C, Composite raster plot merging raster plots from all cells (15 sessions from 13 cells), laid on top of each other. The y-axis was adjusted according to the length of the recording because the time it took before the Purkinje cell CR had been extinguished varied from cell to cell. D, Normalized raster plot based on all cells trained with a single stimulus pulse. The darkness of each square in the raster plot represents the average simple spike frequency in a 10 trial, 10 ms bin divided by the average background frequency in the same bin. E, Line diagram illustrating changes in simple spike firing in different parts of the CS–US interval during training. Whereas there is little change in simple spike firing in the first 100 ms of the CS US interval, the latter part of the CS, and especially the last 100 ms of the CS, is associated with a substantial increase in simple spike firing during trained. Averaging the activity in the whole CS period also reveals an effect of training on simple spike activity. F, Box plot showing how much cells increased their firing in the whole CS during training with a single-pulse stimulus. The change in simple spike firing was calculated by subtracting the average simple spike firing in the last 5% trials of each cell with the activity in the first 5% trials of each cell.
- Figure 3.
Raster plot depicting simple spike firing in a single cell throughout several cycles in which different numbers of stimulus pulses were used as teaching signals. When found, the cell had already received 450 CS and US presentations, which explains why the acquisition of the Purkinje cell CR was seen after <50 trials. Switching from a burst-like teaching signal (two sets of five pulses at 500 Hz) to a single pulse resulted in a typical extinction process; i.e., the simple spike pause response during the CS disappeared. Going up to two pulses had no effect on the Purkinje cell CR, but going up to three pulses resulted in swift reacquisition of the Purkinje cell CR. Finally, going back to one pulse again resulted in extinction.
